Various methods and systems are available for collecting three dimensional data for volumetric digitization of a three dimensional object. This data can be obtained from non-contact devices such as a laser scanner, or camera based Moire interferometry systems. These systems have a problem that they cannot collect data from regions which are out of the line of sight. Therefore, the object from which the data is collected must be oriented in different positions so that parts of the object which are invisible to the data collection device from one orientation will be visible in another, as illustrated in U.S. Pat. No. 4,894,551. This, however, creates a problem with integrating the data sets which have been collected from different orientations.
One solution to the problem of three dimension data collection is use of a device such as described in U.S. Pat. No. 5,139,339. However, this device is destructive, the data is collected but the part is destroyed in the process. For many applications, part destruction is not a viable option.
Another possibility is to very carefully determine precise part orientation during part setup before data collection with some specialized equipment such as a rotary table. However, precise part orientation is very difficult to achieve.
Another method requires a part to have several locating features such as spherical balls. Coordinate measuring machines are used to accurately determine the center of these balls, and this information can be used to determine coordinate transformations to transform data from one coordinate system to another. A touch probe and operator action is required to find several points on the surface of each ball. Standard mathematical techniques can then be used to calculate the ball's center and radius.